In some engine applications, a shielded ignition system is required to meet hazardous area requirements (i.e., to prevent ignition of gases surrounding the engine) or to prevent electrical noise/interference with surrounding electronics (e.g., on aircraft). Some shielded ignition configurations use shielded spark plugs mounted to the cylinder head and connected via flexible shielded secondary leads to remotely mounted ignition coils. While such configurations permit mounting of ignition coils away from the high temperature high vibration conditions associated with mounting to the engine valve cover, such configurations also require use of shielded spark plugs, which are generally more expensive than standard spark plugs and are available in more limited configurations. In other shielded ignition configurations, an integral spark plug is mounted to the cylinder head and connected via a shielded spark plug adapter to a flexible secondary lead coupled to a remotely mounted ignition coil. Again, however, integral spark plugs are generally more expensive than standard spark plugs and are available in more limited configurations. In still other shielded configurations, an integral spark plug is mounted to the cylinder head and connected directly to a shielded ignition coil. These configurations suffer from the problems associated with integral and/or shielded spark plugs. Also, the cantilevered mass of the coil places stress on the spark plug and subjects the coil to increased vibration loads, among other things. Also, in some applications limited space prevents direct connection of the ignition coil to the spark plug. In still other shielded configurations, a conventional or standard spark plug is mounted to the cylinder head and connected via a shielded spark plug extender to a valve cover mounted ignition coil. While these configurations permit use of standard spark plugs, the mounting of the ignition coil to the valve cover exposes the coil to a high temperature and high vibration operating environment, reducing the useful life of the coil and degrading the overall performance of the ignition configuration.
Consequently, it is desirable to provide an ignition configuration which permits use of standard spark plugs, but does not require mounting of ignition coils to the valve cover (i.e., permits remote mounting of the coils to reduce temperature and vibration exposure of the coils).